Robot assemblies are an important component in automation, especially in manufacturing facilities and manufacturing equipments. For example, in the semiconductor industry, robot arms are used to handle semiconductor wafers, flat panel display, LCD, reticles, masks, or carrier boxes.
In the semiconductor fabrication facility, robot can be used to transport workpieces, typically stored in carrier boxes, from one location to another location, from one equipment to another equipment. In a process system, a robot is typically used to remove the workpieces from the carrier boxes, and then loaded into a loadlock. Another robot can be used to move the workpiece from the loadlock into a processing chamber, and from one processing chamber to another processing chamber. Thus within a processing system, there might be a plurality of robots, each one is designed for a particular task. The processing system could be a deposition system, an etch system, a lithography system, a metrology system, an inspection system, an implantation system, a treatment system, or any workpiece processing system.
Another type of equipment is supplemental equipment such as a stocker, designed for storing the workpieces until needed, or a sorter, designed for sorting the workpieces into certain desirable order. In a typical bare stocker system, a robot is typically used to remove the workpieces from the carrier boxes, and then loaded into a loadlock. Another robot can be used to move the workpiece from the loadlock into a storage chamber, where the workpieces are stored without the original carrier boxes. For box stocker system, the workpieces are stored together with the carrier boxes, without the need for removing them out of the carrier boxes.
There are different robot arms for handling different workpieces. For example, semiconductor wafers can be handled from the backside, thus a typical robot arm has an end effector to support the wafer. The wafer usually rests on the end effector, held by either gravity of vacuum suction. For reticles, backside handling is not advisable since it might cause damage. Thus grippers are typically used to handle reticles at the edge.
To improve the efficiency of the fabrication facility and to improve the throughput of the equipment, robots with dual end effectors have been employed to transfer semiconductor wafers. Typically, the two ends of the dual end effector are similar, allowing the transfer of two identical wafers.
With the advancement of semiconductor processing, increasing emphasis is being placed on reticles. Critical defects on reticles are now in the same order of magnitude as defects on wafer, because even reticles have a higher tolerance for critical dimension as compared to semiconductor wafer, their affected area is much larger.
Reticles and reticle carrier boxes has few standards, especially for automation handling, perhaps because of the variety of reticle sizes used in the fabrication facility. And partly because of this lack of standards, many designs for reticles, containers, and boxes are in use in the facility. Reticle handling thus includes special fixtures or cassettes, and typically requires different reticle end-effector and clearances, resulting in multiple, custom end-effector, grippers and automation designs.
One reticle handling mechanism includes switchable arms with a docking station to store various kinds of grippers. Changing arm could reduce throughput, generate particle and reduce yield and reliability of robot arms.